Revenue (Details) - USD ($) $ in Millions	3 Months Ended
Revenue (Details) - USD ($) $ in Millions	Mar. 31, 2026	Mar. 31, 2025	Dec. 31, 2025
RTO Revenue	$ 47.2	$ 37.6
RTO Capacity Revenue	2.1	0.3
Revenues	338.7	252.1
Subsidiaries [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	336.0	248.6
Contract with Customer, Asset, before Allowance for Credit Loss	174.0		$ 157.4
Other Revenues [Member]
Other non-606 revenue	2.7	3.5
Wholesale Revenue [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	16.1	9.2
Retail Revenue [Member] \| Utility [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	270.6	201.5
Retail Revenue [Member] \| Utility [Member] \| Residential Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	179.8	136.7
Retail Revenue [Member] \| Utility [Member] \| Commercial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	56.8	39.8
Retail Revenue [Member] \| Utility [Member] \| Industrial Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	20.9	15.7
Retail Revenue [Member] \| Utility [Member] \| Governmental Revenue
Revenue from Contract with Customer, Excluding Assessed Tax	9.6	7.0
Retail Revenue [Member] \| Utility [Member] \| Other Revenues [Member]
Revenue from Contract with Customer, Excluding Assessed Tax	$ 3.5	$ 2.3